Thermoelectric elements such as thermoelectric generators or Pertier elements advantageously have high thermoelectric conversion efficiencies, are durable; and are efficiently produced at low cost. Materials such as BiTe, SiGe, PbTe and cobalt oxide have all been proposed and intensely investigated as thermoelectric conversion materials prepared from inorganic materials. Several such inorganic materials have been found to have practical properties. However, of these materials, some materials have to be produced through complicated processes, and some are toxic or create toxic byproducts.
Organic thermoelectric materials such as electroconductive polymers are usually easily processed and are generally safe. However, it is generally thought that their thermoelectric conversion properties are not comparable to inorganic materials. Polyanilines have been described as electroconductive polymers that could be used as thermoelectric materials (Japanese Unexamined Patent Publication (Kokai) No. 2000-323758 and Japanese Unexamined Patent Publication (Kokai) No. 2001-326393). Japanese Unexamined Patent Publication (Kokai) No. 2002-100815 describes a polyaniline in which the molecular structure is extended when dissolved in an organic solvent. A substrate spin coated with the solution produced a thin film of a thermoelectric conversion material. However, given the production process, production of practical amounts would be complicated. Japanese Unexamined Patent Publication (Kokai) No. 2003-332638 discloses a poly(3-alkylthiophene) as a thermoelectric conversion material. The reference describes that when the thermoelectric conversion material is doped with iodine, the Seebeck coefficient and electrical conductivity are increased, and as a result the thermoelectric conversion properties are improved. A polyphenylenevinylene and an alkoxy-substituted polyphenylenevinylene are disclosed as thermoelectric conversion materials in Japanese Unexamined Patent Publication (Kokai) No. 2003-332639. The polyphenylenevinylene doped with sulfuric acid and the alkoxy-substituted polyphenylenevinylene doped with iodine showed relatively good thermoelectric conversion properties. However, the sulfuric acid-doped polyphenylene-vinylene was difficult to process and lacked stability in an air atmosphere.
Therefore, there remains a need for organic thermoelectric conversion materials that have advantageous properties and can be easily produced.